The present invention relates to Ethernet switches and switching, and more particularly, this invention relates to disjoint multi-pathing for a data center network.
All fabric types (e.g., networking, storage, and clustering) used in data centers make use of support for multiple redundant paths through the network that help to enable high availability of critical applications. In particular, storage traffic, e.g., traffic over Fibre Channel (FC), internet small computer system interface (iSCSI), and/or FC over Ethernet (FCoE), has traditionally used this approach to insure continuous availability of all the storage resources in a data center. Similar requirements may be found in traditional Ethernet networks or server clusters, e.g., remote direct memory access (RDMA), RDMA over converged Ethernet (RoCE), internet wide area RDMA protocol (iWarp), or other similar RDMA protocols. This requirement may be achieved by implementing more than one physically separate network, each network having redundant switches and links. A significant disadvantage of this approach is the administrative overhead associated with configuring, managing, and maintaining at least two separate networks.
This may be somewhat overcome if a single network fabric is implemented which supports multi-pathing. Such fabrics use an alternative to spanning tree protocol (STP), which forces a single path through the network and thus under-utilizes network bandwidth (in the case of bridged domains, STP forces a single multi-cast tree to be available).
There are different types of multi-pathing, depending on whether the multiple paths through the network share common network devices or whether they are completely disjointed from each other. The highest levels of availability are provided by fabrics which support disjoint multi-pathing, preferably in a flat fabric architecture which facilitates virtual machine (VM) migration in highly virtualized data centers.
There are several possible approaches to support disjoint multi-pathing using open, industry standard protocols, all of which have drawbacks. For example, a single transparent interconnection of lots of links (TRILL) fabric covering the entire data center would not function properly unless enhancements to the currently available industry standards are made in order to support disjoint multi-pathing and a flat Layer 2 fabric. Further, there may be some concern as to implementation of TRILL that use proprietary type-length-value (TLV) encoding or which are not based on intermediate system to intermediate system (IS-IS). TRILL uses different paths for unicast and multicast traffic compared with shortest path bridging (SPB). For the vast majority of Internet protocol (IP) traffic, this should not make a difference. However, care should be taken for latency sensitive applications.
Other proposed standards such as SPB would use additional configuration steps to ensure that different paths are in fact fully disjoint and that the server adaptors select the correct paths to use. Further, by using either of TRILL or SPB, a method to ensure redundancy at the network interface controller (MC) or host bus adapter (HBA) and the first hop into the network would be necessary. Thus, the industry is currently lacking a mature standard-based solution to this problem.